Directionally-selective radio receiving system



March 10, 1931. R. s. HOYT 1,795, 7

DIRECTIONALLY SELECTIVE RADIO RECEIVING SYSTEI Filed Dec. 29. 1927 sSheets-Sheet '1 INVTOR z. sip w BY W Y ATTORNEY March 10', 1931. R, s.HOYT 1,795,397

DIRECTIONALLY SELECTIVE RADIO RECEIVING SYSTEM Filed Dec. 29. 1927 3Sheets-Sheet 2 INVENTOR 1 R. S. floyt fiwpn ATTORNEY March 10, 1931. R.s. HOYT DIRECTIONA LLY SELECTIVE RADIO RECEIVING SYSTEM Filed Dec. 29.1927 3 Sheets-Sheet 3 INVENTOR 5.50

ATTORNEY Fatentecl Mar. 10, 1 931 UNITED STATES PATENT OFFICE RAY S.HOYT, OF RIVER EDGE, NEW JERSEY, ASSIGNOR T AMERICAN TELEPHONE ANDTELEGRAPH COMPANY, A CORPORATION OF NEW YORK DIRECTIONALLY-SELECTIVERADIO RECEIVING SYSTEM Application filed December 29 1927. Serial No.243,380.

It is among the objects of my invention to provide new and improvedapparatus and a corresponding method for receiving radio signals from adesired direction with avoidpance of interference from other directions.

Another object is to provide a radio receiving system that shall beadjustable or flexible in design so as to receive efficiently from oneparticular direction with substantially no interference from anotherdirection, or directions, Another object is to adjust the design so asto reduce the effect of random interference over a considerable range ofdirections other than the desired directionof retem of receiving waveantennae adjustable or flexible in design for one or more of thepurposes stated above. Still another object is to provide a. system ofelements comprising two parallel wave antennae in staggered and spacedrelation, with the dimensions and other determining factors of thesystem so assigned that there will be good reception in one desireddirection and exclusion of interferencein another desired direction ordi eetions. All these objectsand other objects of my invention willbecome apparent on consideration of a limited number of specificembodiments of the invention which are disclosed in the followingspecification taken with the accompanying drawings. It will beunderstood'that the following disclosure relates to these examples ofthe invention and that the scope of the invention will be indicated inthe appended claims.

Referring to the drawings, Figure l is a diagrammatic plan view of .asystem of two parallel staggered wave antennae embodying my invention;Fig. 2 is a corresponding diagrammatic elevation of one of these twowave antennae; Fig. 8 is a diagrammatic plan view with certaindimensions and other data indicated as a basis for discussion; Fig. 4 isa diagrammatic plan showing one way of combining the currents receivedover the several antennae for the operation of a single receiver; Fig. 5corresponds with Fig. 4: but has the receiver at the front end insteadof at the back end; Fig. 6 is a diagram ception. Another object is toprovide a sys-.

pensation currents taken from opposite ends of each wave antenna; Fig.6a is a diagram showing compensation for F 1g. 5 in the mannor of Fig.6; Fig. '7 1s a d agram showing another manner of effecting compensationas applied to a system like that of Fig. 4:;

Fig. 7 a shows the same manner of effecting compensation as applied tothe system of Fig.

5; Fig. 8 showsstill another manner of effecting compensation in asystem such as that of Fig; a; Fig. 8a shows the kind of compensation ofFig. 8 as applied to a system like that of Fig. 5; Fig. 9 is a curvediagram giving the measure of advantage forcertain particular examplesof my invention as f xed for example by certain definitely assignedparameters, and Fig. 10 is a similar curve diagram in which theparameters are the same except that the direction for null reception isdifferent.

A wave antenna may be a-comparatively long horizontal conductorextending in a straight line at a moderate height and in a directionnearly the same as that in which maximum intensity of receiving isdesired.

The elementary theory of such a wave antenna is presented in the papersby H. H.-

Beverage et 'al., in the Journal of the A. I. E. E. for March, 1923'(page 258), and succeeding issues. My invention may be embodied in apair of wave antennae inspacecl parallel relation and staggered; thatis, one of them displaced along the direction of their length. Two suchwave antennae are shown in Fig. 1, adapted for reception of radio wavesincomingon the left. These two antennae are indicated as 1 and 2, andcorre sponding parts and data associated therewith are distinguished bythe subscriptsl and 2.

I shall employ the term transducer inthis specification in its usualmeaning of any assembly of apparatus having a set of input terminals towhich input electromotive forces are applied and a set of outputterminals for output currents, these currents being a function of thesaid electromotive forces. Under this broad term may be mentioned as'examples a transformer, a rotary converter, an amplifier, anattenuator, a transmission line,

for a system such as that of Fig. 4, with coma phase shifter. Someauthorities-use the term quadripole instead of transducer.

In this specification I use certain characters, such as T, sometimes torepresent a piece of apparatus, say T for a transducer, and sometimes torepresent an associated numerical measure such as the complex numbcrvalue for the transfer factor of the transducer. In each instance thesense intended will be apparent from the context.

As shown in Fig. 1, combining transducers T and T are situated at theback ends of the antennae 1 and 2. Each transducer enables the ratio j/Iof its output current to its input current I to be adjusted to any valueas regards magnitude and phase. The antenna output currents I and 1 areevidently the transducer input currents. The transducer output currentsj and 7' after having been adjusted to any desired values by means ofthe respective transducers T and T are finally added together in somesuch manner, for instance, as indicated by Fig. 4:. It will be foundthat either one (but not both) of the transducers can be proportionedarbitrarily as regards its transfer factor T or can even be omitted orbe combined with the other; but for symmetry both are retained in all ofthe figures.

Referring to Fig. 3, 8 denotes the length of each wave-antenna, p, thestaggering of the wave-antennae (that is, the amount by which antenna 2is displaced longitudinally with respect to antenna 1), g the spacing(transverse separation) of the wave-antennae, and r the direct distancebetween the two front ends (and hence between the two back ends).VVave-antenna 1 is taken as the reference axis, its front end 0 asorigin of coordinates, and the direction from front to back as positivedirection. Angles are measured counter-clockwise from the reference axis(antenna 1). 8 denotes the angle from the reference axis to the line 7In Fig. 3 there is shown a train of plane electromagnetic waves (radiowaves, or space waves) incident at any angle 0, measured from thereference axis to the direction of propagation of the radio waves alongthe earths surface. f denotes the horizontal component of the electricforce of the radio waves at the front end of antenna 1, and f thecorresponding simultaneous value at the front end of antenna 2; theseelectric forces are along the direction of incidence (that is, thedirection of propagation in space).

As explicitly indicated by Fig. 1, each antenna is terminated at itsfront end in an arbitrary impedance 1V, and at its back end in atransducer which presents to the waveantenna an arbitrary impedance Z.For simplicity, the front-end terminal iinpedances are not shown in Fig.3, but they are to be regarded as present there. (In most practicalapplications, Z and V would be made equal to the characteristicimpedance K of each wave-antenna, for simplicity and also for securingdesirable directional characteristics for the individual wave, antennae.I denotes the output current of antenna 1 and hence the input current oftransducer T and denotes the corresponding output current of transducerT and similarly for T and j Evidently these currents are functions of 6;this fact will usually be explicity indicated by employing thefunctional symbols I (6),l (6]),j (6),j (0) ;thus the symbols 1 ,1 j y'are to be regarded as abbreviations of the corresponding functionalsymbols. The fact that these currents depend on the incidence angle 6 ofthe radio waves, may be indicated by saying that these currents iavedirectional properties or characteristics.

The transfer factors T and T of the combining transducers are to beregarded as unlike, in general. They are merely the current ratiosdefined by the equations Z 1 .7: a 172:.72(0)/I2(6) 7 which, of course,are independent of 0.

Finally, the received currents j (49) and i (0) are regarded as beingdirectly combined by simple addition so that, if J (6) denotes theresultant current, then U =7'1( +7 0 tions 2w) an/ a Since the twoantennae are alike and are terminated alike (as regards the impedances Wand Z), it is evident that y denoting the propagation constant of theradio waves along their direction of propagation over the earths surface(per unit length) F 3 shows that Hence, by Equations (8), (7), (8), (9),the resultant received current To establish a a 1 11 a The function G(6)will be termed the group factor (or, more fully, the group directionalfactor). This term is adopted because G(6) does not depend on thewave-antennae themselves, but only on their grouping as represented bythe relative positions of their front ends (or of their backs ends), asspecified by r and 8, and on the ratio T /T of the transfer factors ofthe combining transducers.

The functional notation G(6) denotes that 6 is regarded as theindependent variable and hence that the other quantities are regarded.as parameters. It may be observed, however, that 68 could be taken asthe independentvariable, which would correspond to taking the line along1" as reference axis and would apparently reduce the number ofindependent parameters by one; but this reduction is only apparent,because, when the line along 1" is taken as reference axis, theparameter 8 then appears in the formula for the directionalcharacteristic of each wave-antenna alone, whereas it is absent fromthat formula when the direction of the wave-antenna is taken as thereference axis. On the whole it seems best to take the wave-antenna asthe reference axis, so that 8 then occurs as a parameter in the formulafor G(6).

If Y (6) denotes the resultant directional admittance of the array ofthe two waveantennae, combined as aforesaid by means of the transducersTand T and referred 'to the electric force f so that Y (6) is defined bythe equation we ==Z(6) fb then, by (10),

Y. (6)=T Y(6)G(6). (14:) (Subscript a denotes array)..

The directional selectivity of a single wave-antenna, sa antenna 1, withrespect to any arbitrary re 'erence value 6 of 6, is represented by thedirectional ratio p 6) defined by the equation P l '")|a a polar graphof which is the so-called polar diagram representing the directionalcharacteristic of a single wave antenna. (Usually 6,=O). From (15), (4),(5), (6) it is seen that P1( P2( )=P( )?l )i- Similarly the directionalselectivity of the array of the two wave-antennae is represented by theresultant directional'ratio ,,(6) defined by the equation pa e/ e l; Iwhence by (10) and (16) successively, it is seen that q 1 (0) 0 0 6(Pa(6)" W P( )m i where 6) =p (6) =p (6) is the directional ratio of eachwave-antenna. By introducing the group factor ratio 0(6) defined by theequation l )b (18) can be written .as they are sufficiently known in theart; reference may be made to the paper by Beverage et al. mentionedheretofore, where it is shown that the directional ratio (6) of a singlewave antenna can be made decidedly directional by suitable choice of itslength; an alternative exposition of the fundamental theory and formulasfor a single wave antenna Willalso be found in the article by Carson andHoyt, Propagation of periodic currents over'a system of parallel wires,in the Bell System Technical Journal for July,

. 1927, pages 532 to 535. The system disclosed in the presentspecification in accordance with my invention, affords improvement inthat the resultant directional ratio p (6) ,of the spaced staggeredarray of the two waveantennae can be made decidedly more directionalthan the directional ratio 0(6) of each wave-antenna alone; thisimprovement results from the presence in Equation (20) of the groupfactor ratio 0(6) which, as will be shown in the present specificationcan be given particularly desirable directional prop erties by suitablyproportioning the array of the two wave-antennae as regards thestaggering 10, spacing g, and ratio U=T /'I characterizing. thecombining transducers, so that the product 0(6),)(6) will be decidedlymore directional than is p( 6) alone.

By reference to Equation (11) it is seen that the group factor ratio0(6) defined by (19) represents the dependence of the directionalselectivity of the system constituting my invention, on the staggering10 and spacing 9 of the array of the two wave-antennae (or, in otherwords, on 1' and 8), and on the ratio T /T of the transfer factors ofthe-combining transducers. Therefore the properties of the group factorratio 0(6) will now be set forth in some detail. This will beaccomplished by studying the group factor GM) since (TM) is proportionalto GM)[ by Equation (19); it is seen that aM)=l 5 when 0=6 Vith a Viewto writing Equation 11 for GM) in more useful and more signi cant formswe introduce the ratios P, Q, R, defined by the following equations, inwhich 19 denotes the wave length of the radio waves in the direction ofpropagation along the earths surface:

and from Fig. 3 we note that R=P/cos 8=Q/sin S. (24:)

so Also, we let I denote the propagation constant of the radio waves perwave length, so that a therefore denoting the attenuation con- 25 stantof the radio waves per wave length. Furthermore, we let U denote theratio of T to T so that T /T ==U=[ U] 6 (26) "u, therefore denoting thephase-angle of U.

By means of the substitutions (23), (25), (26) Equation (11) for GM)becomes ag denoting angle of or, more fully 45 phase angle of.

Since cos M8)=cos (8-6), it follows from (27) that Similarly Equation(29) shows that these lines, but the major lobe of its polar diagram maybe roughly symmetrical with respect to some intermediate line. It may beadvantageous to so choose the direction of the array of wave-antennaethat the desired signal will come in approximately along thisintermediate line, so that the major lobe of the polar diagram will beat least roughly symmetrical with respect to the direction of thedesired signal. But, in many cases, considerable dissymmetry may bedesirable (to minimize the effects of static and other inter ference)such desired dissymmetry can be at least partially secured by suitablychoosing the direction of the wave-antennae.

The effect of changing 8 to B-t is to rotate the polar diagram ofthrough the angle 5. This follows from Equation (27), since (98 isunchanged when 0 and 8 are each increased by 5. In particular, changing8 S rotates the polar diagram through the angle 25 (since 8=8-28).

Thus far we have dealt with the group factor GM) in a general manner.'We now proceed to show how the system can be so proportioned that theabsolute value GM)] of the 'roup factor will have desirable directionalproperties. (We are not concerned with the phase angle of the receivedcurrent JM), and hence not with the phase angle of GM).)

On referring back to Equations (28) and (29), it is seen that jGM)[depends on no less than five parameters, namely the set a, U I, u, R, 8or the equivalent but more convenient set or, IUI, w, P, Q, (since P=Rcos 8 and Q=R sin 8). The parameter 0:, namely the attenuation constant(per wave length) of the radio waves in space, is of course supposed tobe known, at least approximately. The four remaining parameters U a P, Qare at our disposal and, in fact, are to beso chosen as to yield so faras possible the desired directional properties for |GM)[. Theconsiderations leading up to the evaluation of these parameters will nowbe set forth.

In most practical applications it is desirable that be Zero, or at leastvery small), at some specified value of 6, say 6. Therefore the firstcondition to be imposed will be that GM)1=O. It will be found that thiscondition su'iiices to determine both 1U) and u, that is, the absolutevalue and the phase angle of U=T /T For securing approximately maximumsensitivity at a particular value of 0, say 6 (usually 0 0), it isevidently necessary that the output currents j M) and shall not begreatly out of phase for 6 6. Of course the sensitivity is a maximumwhen thesetwo currents are exactly in phase; moreover the practicaloperation of the system is considerably facilitated if they are inphase. From Equation (32), it is seen that the condition that they be inphase for 6; 6 is that i (6) O, (6) being the angle by which j (6) leads7' (6). However, a value of somewhat different from Zero may in someapplications lead to appreciably better directional characteristics forConsequently (6) will be regarded as specified, but not necessarilyequal to zero. Specification of the values of 6 and (6) enables either Por Q. to be eliminated; it will be found advantageous to eliminate Prather than Q, for a practical reason appearing later.

As a result of applying the foregoing considerations it will be foundthat G(6)i is expressed in terms of the parameters Q, 6, 6, (6). For anyparticular application, the most suitable values of these parameters canbest be determined by plotting sets of curves of r(6)=| G(6)/G(6 )l forvarious sets of values of these parameters, as described ne'ar the endofthis specification and illustrated by Figs. 9 and 10.

Having thus outlined the proposed steps in theevaluation of theparameters fixingthe system, we shall now indicate the details of' thosesteps, and the resulting design-procedure and design-formulas.

Before applying the condition I G(6) ]O, it may be noted from Equation(33) that if G(6)-iszero for 6 6 it is also zero for 6 6 such that see=28, (37) p but (as shown in connection with Equation (50)), as long aso: is not zero, there are no other values of 6 for which G is zero. Ingeneral, 6' and 6 are distinct; but they are coincident when 6 is chosenequal to 8, for then 67 =8 by Equation (37).

From Equation (27), the necessary and sufiicient condition that G (6) bezero for any specified value 6 of 6 (and hence for 6 286), is that Uhave the value U such that I U/ rR cos (a -5) (38) =e ,(:l:b=1, 3, 5,(39) since i l -1 =0. (40) s, Hence, by aid of Equations and (24) I 1:0:12 cos (r-a) (41) 6:24P cos 0'+Q sin 6) I Qt =21rR COS (6'-5) +611"(43) H =27r(P cos 6 Q sin 6') (Mr. (44) These will be employed asdesign-formulas for U I and u. v

A few comments regarding the quantity 6, first occurring in Equation(39), are perhapsdesirable: From it is seen that 791 is the angleof thenumber -11 regarded as a complex numberyhence bean be assigned any oddpositive or negative integral:-

value, as represented in. (39). Thusthe exponent 6% in (39), or the termIn in (43) and (44), corresponds to?) reversals of phase in thetransducers. It will be found that 5 occurs in most of the followingequations, and hence that the form and properties of the physical systemdepend on the choice of b; it will be sufficiently illustrative of myinvention to assume 6 1 for the applications to be hereinafterdescribed.

Since 1//\=f/e and since o, the velocity of phase propagation of theradio waves along the earths surface, is approximately independent ofthe frequency f, it is seen from Equations 44), (21), (22) that 'M' b7ris approximately independent of the frequency. It is advantageous thatthe requisite value of ubnis thus (approximately) independent of thefrequency, since that is a necessary condition for preserving the waveform of a composite wave, such for. instance as a carrier wave modulatedby speech.

If '=(6) denotes the value of (6) when U=U, then by Equation (29),

''=u21rR cos (6 3), (45) whence, by aid of (43) and (44), I

v are (sin 6'sin n+5 (47) #4128111; (0-6) an; (0+0'2a) a a 1 swea Thisequationshows that, so long as a is not zero, G"(6) is zero when andonly when 11/ is zero; and hence, from Equation (49) together with (46),it is seen that G (6) is zero for 6 6 and also for 6=286=6 but for noother values of 6, so long as a is'not zero.

Although, so long as a is not zero, there are two and only two values of6 at which G 6) is zero, designated by 6' and 6" and such that 6' 6 =28,it will now appear that when a 0 there are additional values of 6 atwhich G (6) =0. For, when (1 0, Equation (50) reduces to I I each ofwhich shows that G (6) is zero for those values of 6 such that1//=n(2w), where in=0, 1, 2, 3, If any one of these critical values of 6is denoted by 6,,, then from (49) and (46) it is seen that cos(6'8)cos(6,,,8)=

n/R,(in (),1, 2, 3, (53) Since the value of the left side of thisequation necessarily lies between i2, the applicable values of n lie inthe range 2R$n$2R (54) Hence, when the only applicable value of n is O;whence, by (53), there are then only two values of 6 namely 6 and 6"such that For values of there may be additional values of 6 in general,the complete set of values of 6 includes 6 and 6", these being thevalues of 6 for n i 0.

It is desirable, particularly for engineering applications, to have someknowledge regarding the nature and shape of the graph of I G (6) I inthe neighborhood of the values of 6, which it will be recalled are thevalues of 6 where I G (6) I is zero. For this purpose a formula for theslope of I G"(6) I is useful, namely a formula for d IG'(6) I /d6;however, as will appear below, the absolute value of the slope willsuffice, namely I 03G (6) ,"d6 I For the case =0, it is found fromEquations (52), (49), (46) that In particular, when 6 6 IoZG(6)/cZ6I=27rRIS1I1(6 3)I, (57) because, when 6 6 sin (IV/2) =0 and therefore cos(1///2) =1, by Equation (52). Since, in general, the right side of (57)is not zero, it is seen that the graph of IG(6)I has at 6 6 a cuspminimum, not a stationary minimum; but when 6 =8+n1r (where in 0,1,2,3,then the graph of I G(6)I has a stationary minimum, not a cusp minimum.It is geometrically evident that at each 6 where I G has a cuspminimumthe slope of IG(6)I must be negative at 6=6 and positive-at 6=6and the absolute values of these two slopes must be equal. It is forthese reasons that a knowledge of the absolute value of the slopesuifices.

For engineering applications it is also desirable to know the values of6, say 6 for which I G (6)I has stationary values (that is, a horizontaltangent)-thus not including cusp extrema. Equation (56), by its factorsin (6- 8), shows that one set of values of 6 is given by the equation6s=8+m (in=0, 1, 2, 3, (58),

From Equations (49) and (46) it is seen that the factor cos ('/2) in(56) contributes the additional set of values of 6 given implicity bythe equation b/2R,(ib=1, 3, 5, (59) or, explicity,

6 =8+cos- [cos(68)-b/2R], (60

which gives two values of 6 for each applicable value of Z). Equation(59) shows that the applicable values of 5 lie in the range which willbe employed as a design-formula for P. (This formula shows that bychoosing a sufliciently large value for Z), the staggering ratio P29/)t, could be made so large that interaction between the twowaveantennae would be practically nil, even for small values of thetransverse spacing ratio Q=g/,\; but the directional characteristicswould be less desirable for most applications).

Since R =P +Q (64) '(6) can now be calculated by means of the formulaobtained from Equations (49) and (46). A direct but less'simple formulafor 1/1 (6) could be obtained by substituting (62) into (47) andemploying (49).

By means of Equation (65) together with (52) and (19), the curves inFigs. 9 and 10 were computed. The ordinates of these curves representthe values of the group factor ratio 0' (0) IG (0)/G (6 )I when 6, (thereference value of 6) is taken as Zero, and b=+1. 0"(9) denotes, ofcourse, the

and

value of the function (6) when U is so evalution to 6 1 and 0. On anyone figure, 6',

0 and 0 (6) have the fixed values indicated, while the various curvesthereon correspond to the various values of Q afi'iXed to the curves.-The curves are all for the limiting case of 42 0; for illustrativepurposes and even for most applications, this limiting case representsthe actual case with sufficient closeness, because a is very small. Itwill be noted that 'the shape of these curves depends very considerablyon the spacing of the wave-antennae I as fixed by the parameter Q=g//\.This fact influences the choice of Q; but Q must be chosen large enoughso that the spacing 20 =AQ is sufficient to prevent troublesomeinteraction between the two wave-antennae. It is for this reason thatthe curves have been plotted with Q, instead of P, as parameter; for Pwould seldom be subject to any practical restriction. Inspection ofFigs. 9 and shows that certain of the curves (particularly for Q=O.15and Q=0.20 in Fig; 9, and $7 0.10 in Fig. 10), have very small values ofa (6) over a considerable range of 6, namely a range extendingapproximately from 180 to 0. For certain practical applications, this isa valuable property and is an improvement accomplished by my inventionit is obtained by a proper choice of the spacing ratio 02 07); Forsmaller values of the values of 0(6) over this range of 6 are on thewholemuch largerr I I [Of course each curve in Figs. 9 and 10corresponds to a definite design to a spaced staggered array of twoparallel Wav'enntennte, so far as the spacing and thestaggering and thecombining transducers are c The following table gives the values of theparameters pertaining to the ten designs corresponding to the ten curvesin Figs. 9 and 10.

The values. of, Z), 0, 5 (5), 6, 6} were pre assigned; the resultingvalues of P, R, 8, 6', 0 III I, t0b1r were computed by means ofEquations (62), (63), (64), (58), (42),

(44) respectively.

0, 0 1, 0 0, a (0) =0, U 1 1, 0 0 and 8+ 180 0' Q P R a 0" 0'-04 240 0.333 .333 0. 00 120. 00 00. 240 .05 .305 .300 0. 32 13s. 03 70. 5 240.10 .270 .204 10. 03 150. s7 s0. 0 240 15 .247 .200 31. 102. 00 01.

0 240 20 .213 42. 57 20513 101. 0 220 0 .283 .283 0. 00 140. 00 78. 0220 .05 .205 .270 10. 70 101. at 0 220 1O 247 267 22. 07 184.10" 91. 2220 l5 229 274 -,3 23 2.05. 57 919 220 20 .210 .200 43. 07 227.13 104. 4

oncerned.

fairly comprehensive, are furnished primarily for illustrative purposesin this patent specificatlon. If needed in practical appllcations,similar sets of curves for other values of the parameters can be readilycomputed by means of the formulas furnished in this patentspecification.

From the remarks in the paragraph following Equation (36), it is seenthat any set of curves such as those in Figs. 9 and 10 remain valid whenthe sign of 8 is changed provided also the sign of 6 is changed;this-fact renders it unnecessary to construct separatesets of curves forthe case of 8. 7

With a supposed known (at least approximately), and with b chosen, and9, P, Q, evaluated, the corresponding requisite values for I U I and ucan be calculated by means of Equations (42) and (44) respectively; andp and q by means of (21) and (22), a being SIlPPOSQCl lZDOWIl, ofcourse, since it is the wave length of the radio waves.

It is seen that the foregoing procedure constitutes a systematicsystem-method for proportioning the system as regards the stagger ing 32and the separation q of the two waveantennae, and the ratio U=T /Tpertaining i to the terminal transducers, with the object of securingdesirable directional characteris tics.

tem that will embody my invention in a particular 1nstance,the proceduremay be summarized as follows: Two parallel spaced and staggered waveantenna will be planned, with the spac ng g and-the stagger distance ;0and the ratio T /T as yet undetermined. These desired to be received;also the selectivity for.

that frequency range may be enhanced by interposing appropriate filtersbetween the antennae and the associated receiving apparatus. Appropriatevalues will be chosen and assigned at the outset for 6, 6, 1) (0), b andon Thereupon, one can proceed readily to construct a diagram such as inFig. 9 or 10, making a family of curves by varying the value of Q, theratio of the lateral spacing q to the wave length By means of such adiagram the best value for 9 will be chosen;

Next, the stagger distance p=aP is determined by Equation (62), andthereupon the value of U=T /T becomes definite and ascertainable, asexpressed in Equation ('39) The value chosen for the angle 6? will beone particular direction of especially. bad interference for which it isdesired to makethe reception null. Incidentally, there will resultanother direction-of null reception, which to gether with the assigneddirection, will be To design and adjust a wave antenna sys---symmetrical about the axis passing through the front ends of theantennae.

Moreover, a low intensity of interference over a considerable range ofdirections may be had by suitable choice of Q as, for example, in Fig.9, where it will be seen that from 180 to 240 the ordinates are verymuch less for Q=O.15 than for Q=0.05.

Furthermore, still another arbitrary direction of null interferingreception may be assigned and embodied in the design by practicingcompensation, as disclosed in connection with Figs. 6 to Sc, as will bepointed out presently. Also, in this connection it will be seen thatthis assignment will fix still another direction of null interferingreception, which together with the assigned directions, will besymmetrical about an axis parallel to the wave antennae.

Referring to Fig. i, this is the same as Fig. 1 except that in Fig. 4the transducers T and the T and the receiver are situated at aconvenient common point more or less remote from the back end of thewave-antennw, to which they are connected by means of metallictransmission lines'L and L (each suitably transposed) and transformers Mand M Any dififerences in these transmission lines can be made up in oneof the transducers, or by means of a supplementary artificial lineinserted in series with the shorter transmission line. In setting forththe fundamental theory of such systems, it is convenient to regard thetransmission lines L and L (including any supplementary artificial line)and the transformers M and M as constituting parts of the transducers Tand T Fig. 5 represents a system which does not differ from that ofFig.4 or of Fig. 1 in fundamental principles, but possesses thepractical advantage of enabling the combining apparatus to be'locatednear the front end instead of at the back end. This is accomplished byemploying two wires in multiple for each wave-antenna and terminatingthe back enc of each wave-antenna with a three winding transformer (Nand N respectively) so con nected that the wave-antenna currents comingin over the two wires in multiple are propagated from the back end tothe front end over the metallic circuit composed of the two wires. Ofcourse the same results could be obtained by means of the system of Fig.l employing separate metallic transmission lines for propagating thewave-antenna output currents I and I fromthe back end to the combiningtransducers and the receiver all situated at a common point near thefront end, but the method of Fig. 5 is simpler and more economical andis fr e from possible interaction between the metallic transmissionlines and the wave-antenna It is known that a single wave-antenna can becompensated to secure null reception from any specified angle ofincidence of the radio waves, by suitably combining a small portion ofthe front-end current with the back-end output current. (See, forinstance, Fig. 19 of the above-cited paper by Beverage et al.). Thisfeature of construction and operation is involved in the systems ofFigs. 6 to 8a.

Figs. 6, 7, 8 show three ways for compeneating the system of Fig. 4 soas to secure null reception from any specified angle of incidence of theradio waves, by combining a small portion of the front-end currents withthe back-end output currents, by means of metallic transmission lines (Land L transformers (M and M and supplementary transducers (T and T and TIn Fig. 6 the individual wave-antennae are first separately compensated(by adjusting the transducers T and T respectively), and then theso-compensated wave-antennae are suitably combined by adjusting thetransducers T and T In Fig. 7 the front-end currents are combined witheach other by means of T and T and the back-end currents with each otherby means of T and T and finally the resultant front-end current iscombined with the resultant back-end current by means of T Brieflystated, in Fig. 6 the two antennae are first individually compensated,and then are combined; whereas in Fig. 7 the two antennae are firstcombined (front end with front end, back end with back end), and thenthe combination is compensated as though it were a single wave-antenna.In Fig. 8 the four currents, consisting of the two output currents andthe two compensating currents, are added directly together after havingbeen adjusted to suitable values by means of the transducers T T T Tre-- spectively. The systems in Figs. 6, 7 8 are effectively equivalent;but economically and operatively they differ somewhat from each other.

Figs. 6a, 7a, 8a show the same three different ways of compensationapplied to the system of Fig. 5. Thus Figs. 6a, 7 (1, 8a correspond toFigs. 6, 7, 8 respectively in the same manner as Fig. 5 corresponds toFig. 4.

In some of the systems represented schematically in these figures,transformers would evidently be necessary at certain points in order tosecure a state of balance with respect to earth, as is well known in thecommunication art. These have been omitted from the figures for the sakeof simplicity of description and exposition, but they may be regarded asimplied. In some instances, the transducers would have to be unilateralin order to secure the contemplated results.

It will readily be understood from the foregoing exposition that thediagrams of Figs. 9 and 10 relate not to the design of the individualantennae but to a factor based on the relative arrangement andcombination of two antennae with a receiving system. If each of thesetwo antennae is directionally selective, then they should be placed sothat their polar diagrams will be oriented alike, and preferably so thatthe maximum radii of the polar diagrams will be pointed approximatelytoward the direction fromwhich good signal reception is desired.

I claim:

1.- The method of directionally selective radio receiving which consistsin building up from the radio waves separate, parallel, horizontalwaves, spaced and staggered, and combining them with cumulative efiectfor a desired direction of reception and with low effect for anundesired range of directions other than the said desired direction andwith null effect for a plurality of particular directions other thansaid desired direction.

2. The method of securing maximum reception in one direction and minimuminter ference in another direction with a pair of parallel waveantennae, which consists in adj usting them at a certain spacing g and acertain stagger distance p, and also adjusting the ratio of the transferfactors from said antennae to a common receiver at a certain value U,the values of g, p, and U being optimum for the said character ofreception.

3. The method of securing maximum reception in one direction and minimuminterference in some other directions with a pair of parallel waveantennae, which consists in making them of the best length for receivingat the desired frequency in the direction of their length individually,and also adjusting them at a certain spacing and a certain staggerdistance p, and also adjusting the ratio of the transfer factors fromsaid antennae to a common receiver at a certain value U, and alsodrawing 05 compensating currents through filters from the opposite endsof the respective antennae; thereby getting the desired character ofreception with low intensity over a considerable range of directionsother than the said one direction, and null reception in two assigneddirections other than said one direction, and null reception in twoother directions dependent on said assigned directions.

4. The method of directionally selective radio receiving which consistsin building up from the radio waves separate, parallel, horizontal wirewaves, spaced and staggered each to the magnitude of best individualdirectional selectivity at the desired frequency,

and combining them with cumulative effect for a desired direction ofreception and with low effectfor a range of undesired directions, andwith null effect for at least one particular undesired direction.

5. In a radio receiving system, in combination, two parallel waveantennae spaced apart a certain distance andstaggereda certain distance19, .a common receiver, and transducers between each antenna and thereceiver with a certain ratio U between their transfer factors T and Tthevalues g, p, and Ubeing optimum forI'maximum reception in one certaindirection and also optimum for min; imum interference in another certaindirection. j

6. In a radio receiving system, in combination two parallel waveantennae spaced apart a certain distance g and staggered a certaindistance p, a common receiver, transducers between each end of eachantenna and the receiver with their transfer factors and the values 9and p at optimum for good reception in one certain direction and forminimum interference in a range of directions different therefrom andalso for null reception in two other assigned directions and twoadditional directions, dependent on the assigned directions.

7. In a radio receiving system, in combination two parallel waveantennae, a receiver, and transducers between each end of each antennaand the receiver, said antennae being spaced apart and staggered byoptimum distances, and said transducers having their transfer factorsrelated at optimum values for good reception in one assigned directionand minimum interference in a range of other directions and nullinterference in several particular other directions, of which at leastone is assigned.

8. In a radio receiving system, in combina tion two parallel waveantennae each of best length for directional selectivity at the desiredfrequency, a receiver, and transducers between each antenna and thereceiver, said transducers comprising filters appropriate to currents ofsaid frequency, and said antennae being spaced apart and staggered bydistances optimum for maximum reception in one assigned direction andminimum interference in an assigned range of other directions and nullinterference in at least one assigned other direction and at least oneother direction dependent on the last mentioned assigned direction. r

9. In a radio receiving system, in combination, two parallel waveantennae, a receiver, and transducers between: each antenna and thereceiver,said antennae being spaced apart and staggered by optimumdistances and the antennae being spaced and staggered at properdistances and said transducers having the proper ratio between theirtransfer factors to make reception maximum in one assigned direction andinterference minimum in another assignedl direction.

In testimony whereof, I have signed my name tothis specification this28th clay of December, 1927.

RAY S. HOYT.

